The amygdala is a complex group of nuclei which play a significant is role in the modulation or regulation of many aspect of emotional behavior. The manner in which the individual nuclei interact in their regulating role is unknown. Several neuroanatomical studies of amygdaloid connections have made reference to intra-amygdaloid connections in their Golgi or degeneration studies. However, these techniques are not adequate to determine their exact origin and termination within the amygdala. Recently, the use or horseradish peroxidase (HRP) as a histochemical marker has been used successfully in the nervous system to determine cell bodies of origin of terminal boutons within specific nuclei. The objective of the proposed study is to determine the extent of intra-amygdaloid connections in the cat using HRP as a tracer substance. Electrophoretic injections will be made into the basal and lateral amygdaloid nuclei of the basolateral group and into the cortical, medial and central nuclei of the corticomedial amygdaloid group of nuclei. The cells containing HRP in their cytoplasm and the injection site will be mapped on line drawings of the amygdaloid complex. When each of the nuclei have been injected in the series, a composite diagram will be made. This composite can then be evaluated to determine interactions of each nucleus in the amygdaloid complex. Such a neuroanatomical study may suggest certain functional relationships between different amygdaloid nuclei.